/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.remoting.support;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;

/**
 * Generic support base class for remote accessor and exporters,
 * providing common bean ClassLoader handling.
 *
 * @author Juergen Hoeller
 * @since 2.5.2
 */
public abstract class RemotingSupport implements BeanClassLoaderAware {

    /**
     * Logger available to subclasses.
     */
    protected final Log logger = LogFactory.getLog(getClass());

    private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

    /**
     * Return the ClassLoader that this accessor operates in,
     * to be used for deserializing and for generating proxies.
     */
    protected ClassLoader getBeanClassLoader() {
        return this.beanClassLoader;
    }

    @Override
    public void setBeanClassLoader(ClassLoader classLoader) {
        this.beanClassLoader = classLoader;
    }

    /**
     * Override the thread context ClassLoader with the environment's bean ClassLoader
     * if necessary, i.e. if the bean ClassLoader is not equivalent to the thread
     * context ClassLoader already.
     *
     * @return the original thread context ClassLoader, or {@code null} if not overridden
     */
    @Nullable
    protected ClassLoader overrideThreadContextClassLoader() {
        return ClassUtils.overrideThreadContextClassLoader(getBeanClassLoader());
    }

    /**
     * Reset the original thread context ClassLoader if necessary.
     *
     * @param original the original thread context ClassLoader,
     *                 or {@code null} if not overridden (and hence nothing to reset)
     */
    protected void resetThreadContextClassLoader(@Nullable ClassLoader original) {
        if (original != null) {
            Thread.currentThread().setContextClassLoader(original);
        }
    }

}
